LIPID EXTRACTED BANK BONE BONE - CONDUCTIVE AND MECHANICAL-PROPERTIES

Lipid extraction by chloroform methanol previously has been found to i ncrease the incorporation of frozen bone allografts. This effect may b e because of a decreased immunologic response. In the present study, t he ingrowth capacity into a grafted bone defect was investigated by us ing the bone harvest chamber model in rabbits. In a series of experime nts, defatted and frozen allografts were compared at 1, 2, and 3 weeks ; defatted allografts and defatted autografts were compared at 3 weeks ; and frozen or defatted allografts and nongrafted defects were compar ed at 3 weeks. Evaluation was performed through histology, histomorpho metry, and Tc-99m-MDP scintimetry. The incorporation was better with d efatted grafts: by histology at 1 week, mesenchymal tissue filled the intertrabecular space in defatted specimens and new bone formation sta rted to occur. In contrast, frozen specimens showed a central soft tis sue necrosis surrounded by inflammatory cells. Histomorphometry showed more new bone and more graft resorption in defatted allografts. At 2 and 3 weeks, there was no significant difference in new bone area, but at 3 weeks the scintimetric activity was higher in defatted allograft s, probably caused by an increased remodeling rate. Since defatting di d not cause increased scintimetric activity in previous autograft stud ies, these findings could indicate that there is a detrimental immunol ogic influence on frozen allografts. There were no differences between defatted autografts and allografts. In a second experiment, the bioch emical properties of defatted bone were investigated with a compressio n test on defatted and frozen bone cylinders taken from the calf femor al neck. No difference in biomechanical properties was found. It was c oncluded that lipid extraction produced a graft that was better incorp orated than a nondefatted graft, with no loss of mechanical function.